Potential Prime Testing Flaw in Deno JavaScript Runtime
CVE-2026-49440

7.4HIGH

Key Information:

Vendor

Denoland

Status
Deno
Vendor
CVE Published:
23 June 2026

What is CVE-2026-49440?

Deno, a popular runtime for JavaScript and TypeScript, has a vulnerability in its prime checking functions. Before version 2.8.1, the methods node:crypto.checkPrime and crypto.checkPrimeSync were susceptible to a flaw where no Miller-Rabin rounds were conducted when the checks option was set to its default value of 0. Consequently, these functions only applied trial division by primes up to 17,863, resulting in the incorrect identification of certain composite numbers — specifically those having the smallest prime factor above this threshold — as 'probably prime.' This oversight could lead to significant logical errors in applications relying on accurate prime testing. This vulnerability has been addressed in version 2.8.1.

Affected Version(s)

deno < 2.8.1

References

https://github.com/denoland/deno/security/advisories/GHSA...
x_refsource_CONFIRM
https://github.com/denoland/deno/pull/34391
x_refsource_MISC

CVSS V3.1

Score:
7.4
Severity:
HIGH
Confidentiality:
High
Integrity:
High
Availability:
High
Attack Vector:
Network
Attack Complexity:
High
Privileges Required:
None
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

.